1. Field of the Invention
The present invention relates to a device for detecting a banknote thickness, and more particularly, to a device for detecting a banknote thickness capable of detecting one or more of a thickness of a banknote, a state of a banknote, whether a foreign object is on a banknote, or a type (e.g. denomination or national currency) of a banknote, using an electrostatic capacity property.
2. Description of the Prior Art
In general, a bill validator is installed in a bill counting machine, a vending machine, an automatic teller machine (ATM), or the like, to determine whether an input banknote is proper. For example, the bill validator determines whether a banknote is a new one, old one, damaged one, or forged one.
For reference, the bill validator described in the present invention is used to include a concept covering all of a bill counting machine having a bill validating function, a paper money discriminating machine having a counting function, and the like, as well as supporting bill validation. The bill validator is used in financial institutions, such as banks, cash transport firms, currency exchange offices, credit unions, or post offices, and business units such as casinos, restaurants, department stores, supermarkets, duty-free shops, big-box retailers, or convenience stores dealing with checks and cashes. The bill counting machine includes a banknote thickness detecting device for measuring a thickness of a banknote to accurately count a withdrawal or deposit amount of money requested by a user, or determine whether banknotes overlap or whether a foreign object is on a banknote.
The banknote thickness detecting device measures a thickness of a counted banknote and compares the measured thickness with a pre-determined reference thickness, namely, reference banknote thickness data corresponding to a sheet of banknote, and when the measured banknote thickness data is identical to the pre-determined reference banknote thickness data within tolerance according to the comparison results, the banknote thickness detecting device determines that a sheet of banknote is normally processed.
However, banknotes to be counted may randomly include an old banknote which has been already issued and used, a crumpled banknote, a folded banknote, a wet banknote, a stained banknote, a tape-attached banknote, as well as a newly issued banknote. Namely, the new banknote has a uniform thickness, but an old banknote may have a different thickness according to a state thereof, and in particular, in case of a tape-attached banknote, it may have a greater thickness in a region thereof in which a tape is attached, although it is a sheet of banknote.
Thus, a ultrasonic sensor scheme or a thickness detection roller scheme conventionally used for detecting a thickness of a banknote may erroneously determine a sheet of old banknote as two or more sheets of new banknote, or conversely, erroneously determine two or more sheets of new banknote as a sheet of old banknote and incurs high manufacturing costs.
A background art of the present invention is disclosed in Korean Patent Application Publication No. 10-2006-0060758 (published on Jun. 5, 2006 and entitled “banknote thickness detecting device”).